1. Field
The present disclosure relates to a method for manufacturing a semiconductor device using a method in which a supporting substrate is bonded to a semiconductor wafer.
2. Description of Related Art
In recent years, rapid advances have been made in achieving more compact size and higher density in semiconductor devices. In accordance with this, there have been demands for reduction in the film thickness of semiconductor elements which are used in devices, and the need for semiconductor wafer thicknesses no more than 100 μm has arisen. If the thickness of a semiconductor wafer is reduced to no more than 100 μm, or if a device is formed using a semiconductor wafer of no more than 100 μm, warping occurs due to the insufficient strength of the semiconductor wafer, and therefore the reduction in the thickness of the individual semiconductor wafer, and formation of a device with same, have been impossible. Therefore, in order to supplement the strength of the semiconductor wafer so as to prevent the occurrence of warping, technology has been developed in which a supporting substrate is joined to the semiconductor wafer, then processing of thickness reduction and device formation are carried out.
The technology of joining the supporting substrate to the semiconductor wafer may, for example, use an organic adhesive, such as a polyimide or epoxy resin, or a low-melting-point wax, to bond the semiconductor wafer to the supporting substrate (Japanese Patent Application Publication No. 2004-64040 and Japanese Patent Application Publication No. H6-29385). With this technology, the semiconductor wafer is fixed to the supporting substrate by an organic adhesive or low-melting-point wax, and reduced film thickness is achieved by cutting or device formation. After cutting or device formation, the organic adhesive is caused to decompose by irradiating light, or the wax is melted by applying heat, and the semiconductor wafer is separated from the supporting substrate.
Possible technologies for joining the supporting substrate to the semiconductor wafer include, apart from the organic adhesive and low-melting-point wax described above, a technique in which the semiconductor wafer is fixed to the supporting substrate by protective tape.
The thermal resistance temperature of polyimide which is used as an organic adhesive is no higher than 400° C., and the thermal resistance temperature of epoxy resin is approximately 200° C. Furthermore, the thermal resistance temperature of low-melting-point wax is no higher than 100° C. Therefore, when it is necessary to manufacture a semiconductor device by carrying out processing including a high-temperature process at a diffusion temperature of approximately 1000° C., then organic adhesive and/or low-melting-point wax of this kind cannot be used since the semiconductor wafer cannot be held in a bonded state on the supporting substrate during this high-temperature process.
On the other hand, protective tape also presents problems with thermal resistance, similarly to adhesive, and is not suitable for manufacturing semiconductor devices which include a high-temperature process such as that described above. Furthermore, in the case of protective tape, there is a risk of causing cracks or chips in the semiconductor wafer due to the adhesive force, when the protective tape is separated.